1. Field of the Invention.
The invention relates generally to cellular window coverings, and more particularly, to a cellular window covering having seamless tubular extruded cells.
2. Description of the Prior Art.
Cellular window coverings are well known in the art. Typically, cellular shading products in this field have been described and realized by beginning with flat material that is sometimes called a web. The flat material is folded and/stacked into some form then bonded along lines or seams which convert it to a cellular, collapsible sheet. This type of window covering provides energy-efficiency, beauty and ruggedness. Cellular window coverings have experienced strong sales even though they are relatively costly when compared with ordinary pleated or roller shades. They have been available mostly in non-woven fibrous materials. Non-wovens are less energy-efficient in this use than continuous fibers because of air permeability, but can be produced in many colors and textures for aesthetic appeal, resembling woven cloth which is much more costly than non-wovens. The use of fibrous material also aids in flexibility, much like stranded wire vs. solid, which is essential for collapsing/expanding multiple cells in a window covering with reasonable applied force. Film also suffers from a lack of porosity compared to fabrics, a disadvantage because porous surfaces along a bonding material form bond lines of consistent width and grip. Bonding material between two films must spread laterally and small variations in deposition typically become large variations in line width in the substrate porosity. Once bonded, smooth films must rely only on surface tension, making the bonds weaker than in porous materials where a mechanical interlock of fibers and bonding material can occur. This is especially of concern in this field, where each cell hangs from the one above (in a window) and the load on the bond is one of peeling, as opposed to tensile-normal or shearing. Peeling is the most difficult load to resist for adhesion-only joints. Notably, early developments which led to prior art type cellular window coverings began with cells formed from folded film strips. However, difficulties in bonding and aesthetic objections to the visually, and acoustically, hard film surfaces led to the adoption of the non-woven material now standard for conventional cellular window coverings.
Conventional cellular window coverings have been produced by various methods.
One type of cellular window covering is made from two flat sheets of material which are pleated and then glued face to face at the apex of the folds to form the cells. Thus created, the cellular window covering need only be cut to the desired length to match the window in which it will be installed. Some examples of this type of cellular construction are described in U.S. Pat. No. 4,861,404 to Neff and U.S. Pat. Nos. 4,673,600, 4,677,012 and 4,685,986 to Anderson.
Another type of cellular window covering is constructed by folding over the edges of flat sheets of material and gluing the free ends to form a cell, or multi-cellular structure, and then stacking and gluing the cells on top of each other to form the cellular window covering. The cells can be cut to the width of the window in which it will be installed. Some examples of this type of cellular construction are described in U.S. Pat. Nos. 5,701,940 and along alternating glue lines between sheets of material can be joined this way to form multiple honeycomb shaped rows of cells or a row of cells can be cut at a bond line if a single row of cells is desired. The cells can then be cut to the width of the window in which it will be installed. Some examples of this type of cellular construction is described in U.S. Pat. Nos. 4,388,354 and 4,288,485 to Suominen and U.S. Pat. No. 5,228,936 to Goodhue.
Another method of producing a cellular window covering is disclosed in U.S. Pat. No. 5,193,601, to Corey, et al., in which a multi-cellular collapsible window covering is made from a continuous sheet of flexible material. The sheet of flexible material is pleated in a manner to create permanent folds in the material at regular intervals in alternating directions so that the material collapses easily into a compact stack. Bonds between adjacent folds in the pleated material are formed either by welding or adhesive or other bonding agents along lines parallel to and equidistant from both sides of the pleats.
However, each of the aforementioned types of cellular window coverings are produced by methods which involve folding and gluing together flat sheets of material. A less complex and lower cost method of producing a multi-cellular collapsible window covering can be realized by producing a tubular extrusion which is cut into sections having the desired length. The extruded cells are then stacked and bonded together to create a length of joined tubular cells which forms the fabric for the window covering. Compared to conventional cellular window coverings, such an extrusion process provides all of the benefits and appearance of conventional cellular window coverings but at a lower cost, improved energy efficiency and increased variety of surface finishes. Additionally, this is done without sacrificing any of the durability or benefits of known cellular window covering constructions.